The invention relates to a semiconductor arrangement including a semiconductor device and a connecting element, and to a method for producing a semiconductor arrangement.
To achieve high ampacity, power semiconductor arrangements, e.g., power thyristors or power diodes, usually include an extensive semiconductor element. The semiconductor element includes a semiconductor body, e.g., a wafer, substantially consisting of a semiconductor material, e.g., silicon or silicon carbide. The semiconductor body may include metallizations for forming electrical contacts, electrical lines, field plates, etc.
For electrically contacting a contact face of the semiconductor element, highly conductive connecting elements like disks made of copper, aluminum or other metals and alloys thereof are used. One or more of such connecting elements are arranged adjacent to one another and are pressed against one another and against the contact face to form pressure contacts. Instead of applying pressure for the connecting elements contacting each other and the semiconductor element, the respective elements may be joined fixedly.
Generally, the expansion coefficients of a semiconductor element and of a metallic connecting element differ from one another. During normal operation, the temperature of the semiconductor device may increase from ambient temperature to high temperatures, e.g., 60° C. to 125° C., which causes thermo-mechanical stresses between the semiconductor element and the metal of the connecting element. Under certain circumstances, variations of temperature between −40° C. and +160° C. may occur. In a worst case scenario the semiconductor element may crack due to these thermomechanical stresses. The strength of the stress increases with the area of contact between the semiconductor element and the metal. For example, in high power semiconductor arrangements, the semiconductor element may be a wafer having a diameter of, e.g., more then or equal to 4 inches, 5 inches or even 6 inches.
For a pressure contact, a further problem caused by a different thermal expansion is abrasion that occurs due to a relative movement between adjacent pressure contacted components if the arrangement undergoes large number of temperature cycles.
Typically, such semiconductor devices include two contact faces being arranged on opposite sides of a semiconductor body. Each of these contact faces may be electrically contacted in a way as described above.
The problem of cracking and abrasion may be overcome by inserting a compensating element between the semiconductor element and the connecting element, where the compensating element may be a disk made of molybdenum. Molybdenum is tougher than copper so that the thermomechanical stress affecting the semiconductor device is reduced. However, thick compensating elements increase the costs for producing the semiconductor arrangement and its weight.
For these and other reasons, there is a need for the present invention.